I have started learning data communication and I'm not able to grasp certain topics.
(i) I know that analog signals are continuous and digital signals are discrete. Analog signal are represented by a continuous time-varying quantity like voltage. How are digital signals represented in actual practice? I mean to ask how are the 0s & 1s actually represented/transmitted over a transmission medium? Are they represented by a sudden spike then staying stable and then a sudden fall of the time-varying quantity like voltage?
(i) I know bandwidth is the range of frequencies that make up a composite analog signal. So, if there are two analog signal with frequency 5 Hz and 10 Hz making up a composite signal, will it's bandwidth be (10-5=) 5 hz?
(ii) When we say bandwidth of a transmission medium is 5 hertz, do we mean to say that it allows any composite signal to pass through it, in which difference between the upper frequency and lower frequency making up the composite signal is 5 Hz?
(iii) Can we define bandwidth of a single sine analog signal?
(i) Are digital signal nothing but just superimposition of theoretically an infinite number of analog signals? If yes, then why and how?
(ii) How do we define frequency and bandwidth(in Hertz, not bps) of a digital signal?
Sorry if these questions seem a bit too easy for many but as a self-learner with no college help, It's quite tough for me. Thanks in advance.